AC 20amp breaker trips mid day

[Haycamper]

Just came from Vegas 103 deg with no AC problems. At our new location which is also about 103 deg, the ac compressor would cycle and the fan would stay on with the thermostat on auto. Now it trips the breaker. Last night when it was 90 deg I measured the voltage drop and it went from 120 AC off to 107 with AC on. Before I measured the voltage drop it was running very quiet/slow. Today it's only 80 deg and was able to borrow an amp meter at its drawing 15.1 amps. I can't figure out if it's the campsight voltage or my ac. Any help?

[3_tons]

Myredracer:

“107 volts is getting very low. Low voltage causes an AC unit to draw more current. Anything below 105 volts can result in damage to the AC unit over time. Not what you want to hear, but you should probably stop running it. An autoformer would cure that problem.”

Usually YES, but it’s possible to cite ‘a few’ outlier scenarios where an autoformer might be just a paperweight - consider the low a available potential when operating near the upper limits of a 30a pedestal’s amperage...In this case, I simply reduce my power demands (e.g. shutting off converter charger, etc) to allow the autoformer necessary headroom to function properly... An autoformer is not a substitute for poor power management, and with only 30a to work with.....

I also have a Soft-Start installed (as an alternative to a properly sized and functioning capacitor), but in ‘my case’ have found the autoformer a better solution...I would note too that (try as I might), I find it somewhat odd that the manufacturer will not divulge what makes it work...In search of a solution, this admittedly didn’t keep me from trying it though...

[wa8yxm]

3 tons wrote:


In order to make long distance transmission of electricity efficient and affordable Nikola Tesla figured out that AC was the way to go...So when voltage goes UP current is proportionally driven down, and wires that are used get waaaay smaller... So how does use of an autoformer cause the pedestal CB to trigger open, and why does the autoformer ‘make possible’ the use of my honda genny while loafing along under LOAD when in the eco mode??....Maybe Tesla got it awfully wrong...

You have several things. Volts, Amps. VOlt-amps and watts that are all related.

On the LOAD side. For an inductive load. IN THEORY higher voltage = lower amps. but it may wind up being lower power factor so the amps may not go down as much as you anticipate.

But the Park side of the autoformer. Well if the thing is upping the volts so your A/C is happy then on the park side watts (or rather volt-amps) in much equal or exceed volt-amps out

So 10 amps at 120 volts is 1200 volt amps

Drop the voltage (Park side) to 100 volts. and you need 12 amps to get to 1200 volt amps. That simple.

Now do not even ask me to explain the difference between Volt-amps and Watts.. That's at least a year of collage above you.

[myredracer]

107 volts is getting very low. Low voltage causes an AC unit to draw more current. Anything below 105 volts can result in damage to the AC unit over time. Not what you want to hear, but you should probably stop running it. An autoformer would cure that problem.

If you have a voltmeter, you should be monitoring voltage over the day. It could very well drop even lower at times. Turning off everything you can inside may or may not help a bit. If the entire CG is low at 107 volts, you're kinda stuck tho.

If you can, sometimes moving to another site in a CG/RV park can help. Look for a remote panel or transformer on the ground and get as close as possible to it and voltage can be better due to lower voltage drop in CG wiring to sites.

Note that the 20 amp breaker in the panel may be adjacent to the 30 amp main. Breakers generate heat and more heat as the current they handle increases, due to the bi-metal element inside. Both breakers are also inside a confined space in the RV panel, which is different than the panel in a house. Not the greatest of solutions and as crazy as it sounds, I have heard of some running a fan directly at the panel to cool the breakers down.

Circuit breakers in a confined space aren't really designed to run non-stop for long periods of time, although according to a circuit breaker time-current graph, can operate indefinitely up to a max. temp of 30 degrees C. Heat is the issue.

Also note that an AC unit draws 50-60 amps on initial start-up and if the voltage is already low can cause an AC unit to struggle to start and as well, can also cause damage to the AC unit.

A PI EMS unit will shut you down at 104 volts if you had one.

[3_tons]

“True, I didn't say. I read the pf with a kill-a-watt. I also have a scope displaying voltage and current and observed that it confirmed the kill-a-watt result in terms of trend, but can't get a precise value from it. I'm often skeptical of raw theory and rules of thumb, which is why I measure things. One rule of thumb is that induction motor power factor improves as the load is increased, and the air conditioner motor at a lower voltage would seem to be more heavily loaded, leading to an improved power factor. Best way to prove me "wrong" would be to have actual measurements. I'm surely capable of making a mistake, but I do endeavor to be careful and use multiple instruments whenever able to(the kill-a-watt and scope in this case). “

Be advised that I’m far more driven to have a sentient discussion as a bridge to consensus than to prove someone here wrong ... Having said that, in my view a kill-watt meter (which I occasionally use) is not a sophisticated enough device to get ‘a reliable’ p/f reading, and that instruments that can do this more accurately will cost waaay more than the average user is willing to shell out (However, there’s formula to do this as well - )....JMO

As per the oscilloscope matter, common electrical convention (not ‘raw theory’) IS that when voltage starts to lag current the p/f is thereby reduced due to the creation of heat (wasted energy) thus a departure from unity...This lag is referred to as reactance and can develop (though in different ways) in inductive or capacitive applications and must be countered to avoid a reduction in power factor...To help make this discussion less anecdotal I’ve purposefully punted to standard convention rather than treatise or raw theory....Again, JMO

[MEXICOWANDERER]

Breakers are heat reactive. Both DC and AC.

When the breaker trips, is it hot to the touch? I've changed so many heat-aged breakers I have lost track. And it's because "home" is never cool. I always have on hand a nearly new 20-amp breaker that I use for testing.

Just a thought -

[road-runner]

pianotuna wrote:
road-runner,

I hope you did not operate the unit long at 98 volts.

What happens to the "numbers" after the AC has been running for many hours?

My own "wattage" goes up and up as the ambient temperature gets warmer. It starts at about 1200 and I've seen as high as 1900 watts.

I ran the air conditioner at a bunch of different voltage points until the current draw became fairly stable, in the 10 to 15 minute ballpark. No dispute from me that it can climb for hours. I found this out running the air conditioner from the eu2000i with no issue starting and running it, then having the power draw sneakily climb through the generator's rated load after a while.

3tons wrote:

But you didn’t say how you are determining the p/f...

True, I didn't say. I read the pf with a kill-a-watt. I also have a scope displaying voltage and current and observed that it confirmed the kill-a-watt result in terms of trend, but can't get a precise value from it. I'm often skeptical of raw theory and rules of thumb, which is why I measure things. One rule of thumb is that induction motor power factor improves as the load is increased, and the air conditioner motor at a lower voltage would seem to be more heavily loaded, leading to an improved power factor. Best way to prove me "wrong" would be to have actual measurements. I'm surely capable of making a mistake, but I do endeavor to be careful and use multiple instruments whenever able to(the kill-a-watt and scope in this case).

[3_tons]

road-runner wrote:
Hard for me to tell what some of the posts are saying. I'll throw in that from actual measurements I made on a 13.5 kbtu Dometic air conditioner, in the voltage range of 98 to 122, I found the following:

-As voltage goes down, current draw increases
-As voltage goes down, power factor improves. Worst case was .93 at 122 volts.
-As voltage goes down, total power consumption goes down

With this particular air conditioner, my take is that boosting the voltage is good for the air conditioner, at the expense of slightly higher power consumption.

“As the voltage goes down, the power factor improves”

Wrong, as the voltage goes down, the sinusoidal relationship between current and the voltage begins to widen thereby worsening the power factor - in the ideal, the power factor should be at 1, this is what the capacitor corrects for to keep this relationship in phase (while discharging at 180 deg of sag) and also why its important to use the ‘right sized’ capacitor to overcome this reactance...But you didn’t say how you are determining the p/f...

BTW, at 98v your air conditioner may start to think its a toaster!!

[pianotuna]

road-runner,

I hope you did not operate the unit long at 98 volts.

What happens to the "numbers" after the AC has been running for many hours?

My own "wattage" goes up and up as the ambient temperature gets warmer. It starts at about 1200 and I've seen as high as 1900 watts.

[road-runner]

Hard for me to tell what some of the posts are saying. I'll throw in that from actual measurements I made on a 13.5 kbtu Dometic air conditioner, in the voltage range of 98 to 122, I found the following:

-As voltage goes down, current draw increases
-As voltage goes down, power factor improves. Worst case was .93 at 122 volts.
-As voltage goes down, total power consumption goes down

With this particular air conditioner, my take is that boosting the voltage is good for the air conditioner, at the expense of slightly higher power consumption.

[3_tons]

With or without the autoformer apparent power should be the same, but with the autoformer ‘true power’ stays within design parameters thereby safeguarding the compressor - it’s this important point that makes the difference.

[ktmrfs]

Haycamper wrote:
The autoformer increases the output voltage but it doesn't increase the output power so the output current actually drops. The autoformer input current goes up when the input line voltage drops. So even though the output current may be 28 amps, the input current could be over 30 amps. The increase in voltage is not free it's not a power station where you can just turn up the boiler.

when your driving an induction motor, as the voltage goes down the current goes up, opposite of what one might think. As voltage drops, the motor "back emf" drops causing current to rise. So in a case like this the autotransformer actually can actually reduce current draw, especially as voltage drops down near 100V when driving a motor.

On a pure resistive load then good old ohms law for pure resistive loads applies.

[3_tons]

Haycamper wrote:
3 Tons
The autoformer increases the output voltage but it doesn't increase the output power so the output current actually drops. The autoformer input current goes up when the input line voltage drops. So even though the output current may be 28 amps, the input current could be over 30 amps. The increase in voltage is not free it's not a power station where you can just turn up the boiler

“The autoformer increases the output voltage but it doesn't increase the output power so the output current actually drops”...

Isn’t this rather self evident, but you dismiss the fact that the ‘power factor’ is corrected to near unity thus the air conditioner sees no (or minor) voltage sag...It’s this voltage sag that can burn out compressor windings...

“The autoformer input current goes up when the input line voltage drops. So even though the output current may be 28 amps, the input current could be over 30 amps. The increase in voltage is not free it's not a power station where you can just turn up the boiler”...

I know of no single rooftop air conditioner that uses that many amps, but thats just me with my smallish truck camper - quite naturally outliers do exist (especially when only on a 30a pedestal) when running multiple appliances, high ambient temps, etc....This is exactly where one should instead opt for a 50a pedestal... Judgement plays a large role here...

BTW, recall that your OP question was in reference to a 20a breaker - just saying...

[Haycamper]

3 Tons
The autoformer increases the output voltage but it doesn't increase the output power so the output current actually drops. The autoformer input current goes up when the input line voltage drops. So even though the output current may be 28 amps, the input current could be over 30 amps. The increase in voltage is not free it's not a power station where you can just turn up the boiler

[Haycamper]

The autoformer increases the output voltage but it doesn't increase the output power so the output current actually drops. The autoformer input current goes up when the input line voltage drops. So even though the output current may be 28 amps, the input current could be over 30 amps. The increase in voltage is not free it's not a power station where you can just turn up the boiler.

[3_tons]

DFord wrote:
Trouble with the a device like the autoformer mentioned is that to increase the voltage, the amperage also increase and you're more susceptible to tripping the pedestal breaker - there's no free lunch and you won't be able to draw more than 24 amps (80%) through a 30 amp breaker for any length of time with it tripping.

In order to make long distance transmission of electricity efficient and affordable Nikola Tesla figured out that AC was the way to go...So when voltage goes UP current is proportionally driven down, and wires that are used get waaaay smaller... So how does use of an autoformer cause the pedestal CB to trigger open, and why does the autoformer ‘make possible’ the use of my honda genny while loafing along under LOAD when in the eco mode??....Maybe Tesla got it awfully wrong...